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Research On Image Watermarking Algorithm Based On Discrete Cosine Transform And Wavelet Domain

Posted on:2012-04-19Degree:MasterType:Thesis
Country:ChinaCandidate:X S DuFull Text:PDF
GTID:2178330332990644Subject:Circuits and Systems
Abstract/Summary:PDF Full Text Request
With the rapid development of computer networks and multimedia technology, digital images, audios, videos and other digital media have been widely applied. We can easily make use of digital equipments to process, modify, and store texts, voices, images and videos. However, the digital copies of films or songs will not damage the quality of the work in the digital age. The problem of information security and copyright protection has been increasingly prominent. In order to prevent people from infringing, pirating or casually tampering digital products, digital watermarking technology, which is combined with protected data and also has the characteristics of authentication and identification in the traditional field of cryptography, has aroused more and more attention and become a very popular field of study. Digital watermarking technology means to embed secret information into the digital audios, images, videos and other digital media in order to protect the copyright of digital products, prove the authenticity and reliability of products, track piracy violations and provide ancillary information about the products. Spatial domain image watermarking algorithms characterized by simple algorithms and low computational complexity usually modify the image pixels directly, but generally they have bad robustness.The paper focuses on the Discrete Cosine Transform and wavelet domain image watermarking algorithms and presents two novel image watermarking algorithms in transform domain after referring to classical literature and concluding merits of various algorithms.As usual, because the watermark information is distributed in the whole image, great distortion and black thin lines exist around the main diagonal pixels while employing a conventional Singular Value Decomposition-based method for extracting and recovering the watermark from the cover image which is attacked. In order to solve the above problem, an improved image watermarking algorithm based on Singular Value Decomposition in wavelet domain is presented in this paper. Firstly, a special binary meaningful image should be constructed and the text information is set in the lower left and upper right corner of the image. In that there is no text information around the main diagonal pixels, a good result can be obtained when we extract and recover the watermark by means of simple computing. Next, the multiplication of matrix is applied to reduce the saving parameters from 3 to 1 to make the algorithm simple. Experimental results indicate that the proposed algorithm is invisible and robust and also eliminate the distortion. Finally, a good watermark extraction is obtained and the algorithm could be employed for copyright protection.Then, this paper proposes another novel blind robust image watermarking algorithm based on Discrete Wavelet Transform and Discrete Cosine Transform. First, the binary meaningful watermark image is preprocessed by Arnold scrambling and Logistic chaotic encryption. Second, after decomposing the cover image into the secondary layer, four bands (LL2, LH2, HL2, and HH2) are selected to embed watermark information. We apply block Discrete Cosine Transform to every selected band and employ an improved method to embed the watermark by exchanging a pair of middle frequency coefficients. The embedded intensity varies with different subbands to enhance robustness and realize blind detection. Finally, experimental results indicate that the algorithm has good robustness to image adding noises, cropping, low-pass filtering, sharpening, JPEG compression, histogram equalization, and so on.
Keywords/Search Tags:image watermark, arnold scrambling, chaotic encryption, discrete cosine transform, discrete wavelet transform, singular value decomposition
PDF Full Text Request
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